This application is a revised competing renewal for a second funding period to support the development and evaluation of fluorescence imaging (FI) in guiding the resection of intracranial tumor. Utilizing quantitative FI (qFI) concepts developed during the first funding period, and realized in the form of an intraoperative probe, concentrations of d-aminolevulinic acid (ALA) induced protoporphyrin IX (PpIX) have been measured quantitatively in vivo in human brain tumors. These results are clinically profound because they indicate for the first time that diagnostically significant PpIX concentrations exist brain tumors which are below the threshold of human visual detection - even in low grade glioma (LGG) - tumors previously found inaccessible with visual FI (vFI), despite the significant clinical impact to be gained from improving their completeness of surgical resection through FI technique. Our overall research plan for continuation outlines clinical and technical/ preclinical studies that will be pursued in parallel - a strategy that has proved to be successful during the current funding period and creates a framework for iterative exchange that informs the clinical and technical requirements for solving the resection challenges facing the surgeon. In the second funding phase of the project, we implement and evaluate preclinically technical advances (in Aim 1) designed to achieve wide-field quantitative FI (qFI) and wide-field depth-detected FI (dFI). We will also enroll patients into clinical studies of ALA-induced PpIX FI (in Ai 2) to generate the data required to determine the probability of tumor for a given quantitative value of PpIX concentration. These studies will set the stage for prospective clinical enrollments (in Aim 3) designed to evaluate the addition of qFI and dFI to visual fluorescence imaging (vFI) when surgical accuracy is evaluated intra- and post-operatively with conventional methods . We will realize the combination of qFI and dFI (in Aim 4) to quantitatively detect PpIX concentration at depth by incorporating spatial light modulation imaging in fluorescence as well as reflectance modes. These techniques will also be extended to emerging fluorophores with excitation/emission spectra covering near-infrared wavelengths, which may ultimately have more potential than PpIX, and to enable simultaneous quantitative imaging of concentrations of multiple fluorophores. By the end of the proposed funding period, we will have implemented and evaluated wide-field qFI and dFI techniques in human surgeries and expect to demonstrate that these innovations improve surgical outcomes when added to vFI in a prospective enrollment of patients with malignant glioma.